1. Technical Field
The present invention relates generally to solenoid actuators and, more particularly, to a dual gain variable control solenoid having two individually wound and controlled coils for actuating a control element and achieving a desired transfer function.
2. Discussion
Pressure control solenoids are commonly used for numerous applications to electromagnetically actuate an armature which in turn forces a valve element to provide pressure control. In automotive vehicles, solenoids are widely employed to control pressure to a clutch to engage transmission clutch elements or to control pressure to a brake element. Pressure control solenoids are also used to control a valve to vary the opening of a valve port between an open and a closed position.
Conventional pressure control solenoids generally include an armature which is actuated by an electromagnetic attraction and an electromagnetic coil wound about a bobbin. A valve element is often displaced by the armature and a return spring often urges the armature in a direction opposite to the direction of the electromagnetic forces. The electromagnetic attraction of the electromagnetic coil and the resiliency of the return spring apply opposing forces to the armature to vary fluid flow through a valve port which is opened or closed by the valve in a cycle.
Dual coil control solenoids are also known. The typical dual coil solenoid generally includes a pair of electromagnetic coils wound about the bobbin and typically applies opposing forces to the armature. Force in one direction urges the armature in a first direction, while the force in the opposite direction urges the armature in an opposite direction. The conventional solenoids are usually controlled to provide on or off current supply to the coil or coils and therefore resultantly, generally provide a pair of valve positions.
Present applications increasingly require good resolution at low control pressures while maintaining the capacity to provide high control pressure in the same application. For example, some applications require more adequate control of the force applied to or displacement of the armature to apply a wide range of forces or pressures to clutch elements in an automatic transmission where varying forces or pressures are desired.
It is therefore desirable to provide for a dual gain variable control solenoid for actuating a control element to achieve a desired amount of force or pressure.
It is further desirable to provide a dual coil control solenoid having independent variable control currents for each coil.
It is yet further desirable to provide a method of operating a dual coil control solenoid to provide dual gain control of the armature.